Now, we have the page up, so next we need to rotate it down back to flat. Rotate it another 90 degrees in the Y direction, this time we need to rotate on the right side of it (so all the text looks right when its rotating down. This gives the illusion that there is a front and a back to the view.

Revision as of 23:00, 17 November 2010

Contents

Introduction

Ok, so maybe you need a page flip animation. There are lots of UIView default animations, that look really good, but my UI designed really busted me and was like "NO, I WANT A BARN DOOR FLIP". Anyway, there isn't a default way that I could find to do this. So I had to take a dive into core animation land and dig deep.

Flipping Open

Aight, so to flip a view open, we take the view, and rotate it using core animation by 90 degrees in y direction around the left side of it. All makes sense right? So, get a UIView as a container and add anything you want to flip onto it.

-(void)pageOpen {
//Make sure the container is visible and remove any other previous animations from it
[uiv_container.layer removeAllAnimations];
[uiv_front setHidden:NO];
[uiv_container setUserInteractionEnabled:NO];
//Sets the anchor point to the middle of the left side
uiv_container.layer.anchorPoint = CGPointMake(0.0f,0.5f);
//Set up a new animation to describe the transform
CABasicAnimation *ba_animation = [CABasicAnimation animationWithKeyPath:@"transform"];
ba_animation.removedOnCompletion = NO;
//This is the time it takes for the animation to complete, here its 2 seconds
ba_animation.duration = 2.0;
//Using different timing functions will change the animation speed at different points. Ex: kCAMediaTimingFunctionEaseIn
ba_animation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear];
//Start from the identity matrix. If you haven't every done 3D programming, the Identity matrix is basically the normal matrix of anything
ba_animation.fromValue = [NSValue valueWithCATransform3D:CATransform3DIdentity];
//Set up the end matrix. Here we are setting it to 90 degrees in the Y direction
CATransform3D t_end = CATransform3DMakeRotation(M_PI/2, 0.0, -1.0, 0.0);
//This value controls the size of the end, modifying it like this makes it get bigger, making it more like a 3D rotation
t_end.m14 = -0.001f;
ba_animation.toValue = [NSValue valueWithCATransform3D:t_end];
//Add the animation to an animation group, this lets us track the animation as it finishes
CAAnimationGroup *ag_group = [CAAnimationGroup animation];
ag_group.delegate = self;
ag_group.duration = 2.0;
[ag_group setValue:[NSNumber numberWithInt:1] forKey:@"Animation Tag"];
ag_group.animations = [NSArray arrayWithObjects:ba_animation, nil];
[uiv_container.layer addAnimation:ag_group forKey:@"Flip View"];
}

Flipping Closed

Now, we have the page up, so next we need to rotate it down back to flat. Rotate it another 90 degrees in the Y direction, this time we need to rotate on the right side of it (so all the text looks right when its rotating down. This gives the illusion that there is a front and a back to the view.